The piano box is a (somewhat polyphonic) paper toy synthesizer with 12 keys, each triggering a tone and an LED. The keys are a set of capacitive sensors, made of copper tape, controlled by an Arduino Mega running the CapSense and Tone libraries. The code for this project, written by Will Byrd and Catarina Mota, can be downloaded here. Please note that the current version of the Tone library has some problems on Arduino 1.0. so it’s best to use version 23 or earlier.